The use of functional neuroimaging to explore cognitive function in welders exposed to manganese

Manganese (Mn)-induced cognitive neurotoxicity is of growing concern. Neuroimaging is undergoing a shift from morphological to functional approaches as new technologies are gradually introduced. Recently, functional neuroimaging modalities including magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), and functional MRI (fMRI), have been applied to evaluate neurological consequences in workers exposed to Mn. Proton MRS has been employed to quantify brain metabolite levels in Mn-exposed workers. We earlier showed that cognitive decline in Mn-exposed welders was associated with characteristic MRS findings. The fMRI data, combined with cognitive task information, indicated that welders may need to recruit more neural resources to their working memory network to compensate for subtle subclinical working memory deficits caused by Mn exposure. The observed correlations between fractional anisotropy (FA) in the frontal white matter obtained using DTI, and Stroop test scores suggested that poor performance in terms of executive functioning was closely associated with lower FA values in the frontal white matter. In summary, MRS, fMRI, and DTI can reveal cognitive deficits in Mn-exposed welders with cognitive neurobehavioral impairments. Functional neuroimaging is potentially valuable when used to study subclinical cognitive deficits caused by neurotoxins.